This invention is directed to a process and apparatus for removing chemical contaminants from groundwater. More particularly, the present invention is directed to a process and apparatus in which vacuum extraction is used to remove soil contaminants from both the saturated and vadose zones. One embodiment of the present invention is directed to a process for removing contaminants from a contaminated area of the ground having a vadose zone and a water table, which comprises providing a borehole in the contaminated area to a depth below the water table; placing in the borehole to a depth below the water table a first perforated riser pipe; placing inside the first perforated riser pipe a second perforated riser pipe; placing inside the second perforated riser pipe a first vacuum extraction pipe with a bottom opening situated within the second perforated riser pipe; placing a second vacuum extraction pipe within the first perforated riser pipe but without the second perforated riser pipe; while introducing a gas into the second perforated riser pipe, applying a vacuum to the first vacuum extraction pipe and applying a vacuum to the second vacuum extraction pipe to draw gases and liquid from the soil into the first vacuum extraction pipe and the second vacuum extraction pipe and transport both gases and liquid to the surface as two-phase common streams through the first vacuum extraction pipe and the second vacuum extraction pipe; forming from the common streams at least one primarily liquid stream and at least one primarily gaseous stream; and separately treating the separated liquid and gas streams. Another embodiment of the present invention is directed to an apparatus for removing contaminants from a contaminated area of the ground having a water table and a vadose zone above the water table which comprises a first perforated riser pipe extending downwardly from the surface of the ground to a level below the water table, a second perforated riser pipe situated inside the first perforated riser pipe and extending downwardly from the surface of the ground to a level below the water table, a first vacuum extraction pipe situated inside of the second perforated riser pipe and having a bottom opening situated within the second perforated riser pipe, a second vacuum extraction pipe situated inside the first perforated riser pipe but without the second perforated riser pipe, a gas inlet for introducing a gas into the second perforated riser pipe, at least one vacuum-forming apparatus in fluid communication with the first vacuum extraction pipe and the second vacuum extraction pipe and adapted to form a zone of reduced pressure in the ground around the first perforated riser pipe, whereby gases and liquid can be drawn from the ground into the first vacuum extraction pipe and the second vacuum extraction pipe and conveyed to the surface as two-phase common streams, and a means for receiving the two-phase common streams and separating the two-phase common streams into separate gas and liquid streams.
Contaminants can exist in subsurface soil and groundwater in the liquid or vapor phase as discrete substances and mixed with and/or dissolved in groundwater and soil gases. Various contaminants can be found in groundwater and soil, such as volatile compounds, including volatile organic compounds, nonvolatile materials, metal contaminants, and the like. Such contaminants can be found and dealt with in the vadose (unsaturated) zone found between the surface of the earth and the water table, at the interface between the vadose zone and the water table, and in the saturated zone below the water table.
At many industrial and commercial facilities and at waste handling and disposal sites, soil and groundwater are contaminated with suspended or water-soluble chemicals, or both. A variety of techniques have been used for removal of contaminants and remediation of affected soil. One common technique entails the excavation and off-site treatment of the soil. Another technique entails saturating the contaminated soil with water in situ, causing the contaminants to be leached slowly from the soil by the water. The contaminated water can then be removed.
Techniques have also been proposed for removing volatile organic contaminants from soil by vacuum extraction. For example, in U.S. Pat. 4,323,122, it was proposed that a vacuum be applied in a borehole at the level of the water table, the assumption being that a contaminant such as gasoline, which is lighter than water, would float on the water table and present a layer that could be drawn off by vacuum applied to the liquid at or around that level. U.S. Pat. 4,323,122 (Knopik) discloses a system and method for recovering organic liquid such as gasoline which has settled on the water table in underground areas. The system comprises a conduit extending from the ground surface to a point just above the water table, a collection head fitted on the lower end of the conduit, a collection vessel connected to the upper end of the conduit, and an exhaust means for creating less than atmospheric pressure in the vessel. The collection head has a liquid impermeable end portion and a liquid permeable intermediate portion for permitting the passage of liquid. The process comprises providing an opening in the ground to a point beneath the surface of the water table, positioning the conduit with the collection head in place so that the liquid permeable wall of the collection head is just above the surface of the water table, connecting the conduit to the collection vessel intake, and exhausting air and other gaseous materials from the vessel to cause liquid to flow into the collection head through the conduit into the vessel.
Others have suggested the possibility of venting soil above the water table (i.e., in the vadose zone) to cause vaporization of the contaminant in the soil, and then drawing off the contaminant in the vapor phase. Groundwater requiring treatment is in such processes conventionally removed by pumping from separate conventional water wells. In situations in which water does flow into vacuum extraction wells, it has been suggested that a second, liquid phase pump be placed either in the well or at the surface to remove the water through a second conduit. For example, U.S. Pat. 4,660,639 (Visser et al.), the disclosure of which is totally incorporated herein by reference, discloses a process for the removal of volatile contaminants from the vadose zone of contaminated ground by extracting volatilized contaminants from the vadose zone by way of one or more vacuum extraction wells. The process entails drilling one or more wells into the subsurface media in the contaminated area, the well being constructed so that fluids in the vadose zone can flow into the well, whereas the liquid in the saturated zone below the water table cannot substantially flow into the well. The borehole and conduit of the well can optionally extend below the water table, in which case the vacuum applied to the upper portion of the conduit will be effective to draw contaminant from the vadose zone, but insufficient to draw a significant amount of water from the saturated zone into the conduit. If it is desired to remove groundwater from below the water table, this removal is accomplished either by a separate sampling device situated in the borehole or through a separate well.
In addition, Stinson, "EPA Site Demonstration of the Terra Vac In Situ Vacuum Extraction Process in Groveland, Mass.", Air & Waste Management Association, Vol. 39, No. 8, pages 1054 to 1062 (1989), the disclosure of which is totally incorporated herein by reference, discloses an evaluation of an in situ vacuum extraction process. The process entails removal of contaminants from the vadose zone by vacuum. Wells are installed in the contaminated vadose soil. A vacuum pump or blower induces air flow through the soil, stripping and volatilizing volatile organic compounds from the soil matrix into the air stream. Liquid water, if present in the soil, is also extracted along with the contamination. The two-phase stream of contaminated air and water flows to a vapor/liquid separator where contaminated water is removed. The contaminated air stream then flows through a treatment system such as gas-phase activated carbon to remove contaminants from the air stream. The clean air is exhausted to the atmosphere through a vent. U.S. Pat. 4,593,760 (Visser et al.), the disclosure of which is totally incorporated herein by reference, and U.S. Pat. No. Re. 33,102 , the disclosure of which is totally incorporated herein by reference, also disclose processes for removal of volatile contaminants from the vadose zone of contaminated ground by pumping volatilized contaminants from the vadose zone using one or more vacuum extraction wells.
"Forced Venting to Remove Gasoline Vapor from a Large-Scale Model Aquifer," American Petroleum Institute, Health and Environmental Sciences Department, API Publication No. 4431 (1984) discloses the results of experiments examining forced venting of air through the soil above a gasoline spill in a model aquifer. Various flow rates and geometries for the venting plumbing were used to determine the most efficient method of removing gasoline from the underground environment and lowering gasoline vapor concentrations in the unsaturated zone above the spill.
"Venting for the Removal of Hydrocarbon Vapors from Gasoline Contaminated Soil," J. Thornton and W. Wootan, J. Environ. Sci. Health, A17(1), 31-44 (1982) discloses the results of an experiment investigating the use of a venting strategy to remove gasoline vapors from contaminated soil strata. A contained gasoline leak was created in a large outdoor facility which simulates soil strata and a static water table. An air flow was established, and vapor samples taken before, during, and after venting were checked for hydrocarbon content.
U.S. Pat. No. 4,892,664 (Miller), the disclosure of which is totally incorporated herein by reference, discloses a method and system for decontaminating water, such as groundwater or process effluent, which is contaminated by small concentrations of dissolved volatile organic compounds. The process includes introducing a flow of the water to an air stripping stage in which the water is directed through the column to air strip organic molecules from the contaminated water, releasing the decontaminated water to the environment, pretreating the organic compounds carrying air in the substantial absence of water through a preheater, passing the heated air through a catalytic stage that oxidizes the organic compounds, and releasing the gaseous effluent from the catalytic stage to the atmosphere. Water containing small concentrations of dissolved volatile organic compounds can also be decontaminated by including an apparatus for retrofitting an existing air stripper for this purpose.
U.S. Pat. No. 4,444,260 (Boyd et al.) discloses a method for the treatment of oil well production streams to process oil-contaminated sand to recover oil therefrom and produce an ecologically acceptable clean sand residue. The process entails separating the production fluid from an oil well having sand entrained therein from a plurality of components, one of which comprises an oil-contaminated sand. The contaminated sand is contacted with a light oil solvent to initiate a solvating action of the oil contaminant. The resulting mixture of oil-contaminated sand and solvent is then contacted with water and the system then gravity separated into discrete sand, water, and oil phases. The oil and water phases can be removed from the sand and the sand phase again contacted with water and the resulting mixture is then subjected to gravity separation to produce separate sand and water phases. The water phase is then removed and the sand passed to a suitable disposal facility.
U.S. Pat. No. 4,730,672 (Payne) and U.S. Pat. No. 4,890,673 (Payne), the disclosures of each of which are totally incorporated herein by reference, disclose a method and apparatus for collecting volatile contaminants from the vadose layer of earth. The apparatus is a closed-loop device which includes one or more contaminant withdrawal wells surrounded by multiple air reinjection wells connected by a conduit. One or more pumps serve to draw volatilized contaminant through the withdrawal well to the connecting conduit where it is captured or neutralized. Residual air from the withdrawal well is urged back into the ground through the air reinjection wells to encourage further contaminant to move toward the withdrawal well for collection.
U.S. Pat. No. 4,945,988 (Payne et al.), the disclosure of which is totally incorporated herein by reference, discloses a process for removing and disposing of or neutralizing volatile contaminants existing in the vadose zone of earth and also in a below ground aquifer. The process includes the injection of substantially oxygen free air into the aquifer to retard the formation of aerobic bacteria and injection of oxygen rich air into the vadose zone to stimulate bacterial growth which aids contaminant recovery. Volatilized contaminants are pulled out of the soil through withdrawal wells which terminate in the vadose zone.
U.S. Pat. No. 4,886,119 (Bernhardt et al.) discloses a process for driving volatile impurities from a ground by means of air by aspirating an afterflow air and impurities containing gases which penetrated through a permeable wall of a shaft in a ground, at one or several locations. In regions of expected high gas contents, air afterflow passages are extended to these regions for supplying the afterflow air, and an adjustable afterflow resistance is arranged in the passages for influencing a negative pressure value and a flow speed in these regions.
U.S. Pat. No. 3,743,355 (Blackwell et al.) discloses a method for withdrawing hazardous gases from a water saturated subterranean formation containing a mineral deposit suitable for mining. The process entails drilling wells through the subterranean formation and withdrawing water from the subterranean formation to establish permeability to gas within the subterranean formation. Gas is then withdrawn from the formation by means of the wells. The method is particularly applicable for reducing the influx of radon into a mine contained in a mineral deposit.
U.S. Pat. No. 1,547,194 (Arbon) discloses a system for elevating oil consisting in packing a well between the eduction tube and casing to cause the accumulation of the gas, arranging valved ejectors in said tube above and below the packing, and regulating the valves to cause successive elevation of fluid in the tube.
U.S. Pat. No. 753,045 (Cooper) discloses a method of obtaining gas from wells containing water with gas held in solution which consists in lifting the water in the well by means of a hydrocarbon gas introduced under pressure into the water column below and collecting the gas liberated from the lifted water.
U.S. Pat. No. 1,291,130 (Purchase) discloses an eduction pipe for air lifts, the cross section of which varies in steps, the maximum cross section being at the bottom and adapted to be submerged, the minimum cross section following the maximum cross section, the section larger than the minimum but smaller than the maximum following the minimum section.
U.S. Pat. No. 2,026,419 (Davidson) discloses an apparatus and process for enlarging the normal subterranean liquid capacity of the supply area of a tube well which consists of oscillating indigenous liquid of the area by pumping forces set up in the tube to dislodge alluvium and simultaneously applying air pressure to remove the alluvium from the well.
U.S. Pat. No. 4,017,120 (Carlson et al.) discloses the production of hot brines containing dissolved gases from liquid dominated geothermal wells by utilizing lift gases of essentially the same composition as the dissolved gases. The lift gas is separated from the produced brine and recycled. Heat is abstracted from the separated brine, which may be returned to the aquifer, processed for its mineral content, or discarded. The gas lift is carried out under temperature and pressure conditions such that the precipitation of minerals from the brine does not occur in the well bore.
U.S. Pat. No. 4,180,980 (Marks et al.) discloses a method and apparatus for releasing for use air that has been absorbed under pressure in sea water or in any other large free body of water. An elongated conduit or other equivalent means is vertically disposed so that air released from its upper end is collected by an open bottom container serving as a reservoir. The interface of the collected air and the submersion level of water within the reservoir is substantially below the free water surface level. A small amount of gas is introduced at the lower end of the conduit so as to rise upwardly through the conduit, thereby carrying water behind it, and to initiate a continuous process in which the rising water is under decreasing pressure, at times increasing temperature, thereby releasing more air, which in turn carries more water behind it. Air from the reservoir can be used as an energy source.
U.S. Pat. No. 4,267,885 (Sanderford) discloses a method and apparatus to optimize and control the production of an oil well which is being artificially produced by gas-lift techniques. The invention is suitable for use with either continuous or intermittent gas-lift operation and can be used with a combination of both. The temperature of the fluid at the wellhead is sensed and used to determine the injection parameter values to optimize well production. In one embodiment, a process control unit is programmed according to the inventive method to interpret the temperature data and to control the gas control valve to optimize production.
U.S. Pat. No. 4,895,085 (Chips) discloses a method and structure whereby contaminated soil is decontaminated in situ by the extraction of vapor from the soil and subsequent destruction of the contaminants contained in the interstitial fluid of the soil by processing the fluid through an internal combustion engine or other suitable combustion means. To achieve this purpose, a means of conducting the fluid from the soil to a manifold system is provided.
U.S. Pat. No. 4,982,788 (Donnelly) discloses an apparatus and method for removing hazardous volatile contaminants from the ground by circulating air between two substantially parallel wells and by removing the vapors of the organic compound from the circulated air using at least one of a condenser and a demister. To enhance efficiency the air is recirculated in a closed loop. The heat output of the condensation process is used to heat the recirculated air. Pipes having openings along only a limited portion of their lengths are placed in the wells and the depth of the openings adjusted to treat one level at a time, thereby preventing shunting of air through more porous soil layers. Flow rates can be equalized by using circumferentially placed induction wells surrounding an extraction well (or the reverse) and by controlling air flow through individual sections of a given level.
U.S. Pat. No. 5,009,266 (Dieter) discloses a method for the in situ removal of mobilizable contaminants, including volatile and semi-volatile organic compounds, from a contaminated unsaturated zone of primarily porous layers of soil. The method comprises pulsatilely injecting heated pressurized steam into a first location in the zone to heat the soil in the zone, and withdrawing the contaminants under subatmospheric pressure from the soil at a second location in the zone. In specific application, the pulsatile injection of steam is used to heat the soil without directly recovering injected steam for a significant period of time until the targeted soil in the zone is uniformly heated to steam temperature. The pulsatile injection directs the heat in particular directions and to particular areas in the soil zone as desired.
U.S. Pat. No. 5,018,576 (Udell et al.) discloses a method for in situ decontamination of contaminated subsurface area by injection of steam into injection wells and withdrawing liquids and vapors from extraction wells under subatmospheric pressure whereby steam is passed through the contaminated area in an essentially horizontal direction. After a substantial portion of the contamination has been removed in this manner, the injection of steam is ceased, but the extraction at subatmospheric pressure is continued, to volatilize and remove the residual water and contaminants trapped in the pores of the soil. The steam injection may be periodically resumed to reheat the area and to replenish the water in the pores.
U.S. Pat. No. 2,605,637 (Rhoades), the disclosure of which is totally incorporated herein by reference, discloses a method of subterranean surveying to determine the liquid levels of a plurality of superimposed fluid bearing strata through a single drill hole. A plurality of tubes are housed within a single drill hole. The tubes are positioned at varying subterranean fluid bearing strata and are used to measure liquid levels in each of the isolated strata.
U.S. Pat. No. 2,925,097 (Duesterberg), the disclosure of which is totally incorporated herein by reference, discloses a tubular member adapted to be positioned in the flow string of an oil or gas well. A plurality of flow tubes are placed within a wellbore for removing well fluids. The tubes comprise a perforate section that prevents cutting out or eroding caused by high fluid pressure or abrasive fluids.
U.S. Pat. No. 4,834,178 (Knecht et al.), the disclosure of which is totally incorporated herein by reference, discloses a process and apparatus for fireflooding with liquid heat transfer media comprising injection of oxidant gas and liquid heat transfer media into a well through separate conduits, the liquid conduit downstream end submerged in a liquid volume, so as to form a seal and prevent oxidant gas migration into the liquid conduit.
U.S. Pat. No. 5,161,613 (Jones), the disclosure of which is totally incorporated herein by reference, discloses a method and apparatus for treating multiple strata in a single operation from a single wellbore which penetrates a treatment interval which, in turn, includes a plurality of strata which, in turn, have different permeabilities. A treating fluid, such as a consolidating agent, acid, or the like, is delivered directly to different levels within a section of the wellbore adjacent the interval to be treated through a plurality of alternate paths which, in turn, lie substantially adjacent to the strata to be treated.
U.S. Pat. No. 5,190,108 (Mansuy), the disclosure of which is totally incorporated herein by reference, discloses the inhibition of biological fouling of water wells by replacing the air in the well column with an anoxic gas such as nitrogen to deprive aerobic bacteria of oxygen. The anoxic gas is applied from a cylindrical tank at the surface and through a gas pipe extending from the tank down into the well casing. The well casing is sealed near the top to prevent air infiltration and maintain a positive gas pressure. The anoxic gas is applied at a slightly positive pressure to maintain the well column filled with it and to prevent air penetration. The gas can be supplied to the well column only or to both the well column and the aquifer so that a blanket of gas in the area of the well inhibits air penetration of the water from the unsaturated cover layer above the aquifer.
U.S. Pat. No. 5,246,070 (Greve et al.), the disclosure of which is totally incorporated herein by reference, discloses a method for completing a groundwater monitoring site including several monitoring points disposed at different depths. The piping includes a single multi-conduit pipe having a smooth, tightly packable outer wall and being composed of individual pipe lengths which are coupled to each other in a sealed relationship. The pipe lengths are subdivided in the longitudinal direction into several conduits by partition walls and are coupled to each other in such a fashion that their conduits are in relative alignment at the junctures and not reduced in area. For the purpose of providing filter sections for the admission of water, individual pipe lengths are provided in their outer wall with filter slots in the area of one or several conduits.
U.S. Pat. No. 5,271,467 (Lynch), the disclosure of which is totally incorporated herein by reference, discloses methods and systems for recovering groundwater, gases and vapors from subsurface locations in a single, integrated operation by applying a vacuum to groundwater recovery wells. Selective recovery of specific contaminants from zones of interest containing high levels of those contaminants is achieved by manipulating the local water table level. Groundwater recovery systems may also utilize eductor systems having venturi nozzles that create a vacuum networked. A plurality of such recovery wells operated using eductor systems may be operated by a single pump at or above grade level. In this fashion, a network of recovery wells may be operated using a single pump and control system. The recovery methods and systems are preferably utilized in association with known contaminant removal systems to provide complete removal of contaminants and improved remediation efficiencies.
U.S. Pat. No. 4,625,801 (McLaughlin et al.) discloses methods and apparatus for the recovery of petroleum origin hydrocarbons from ground water tables at sites of refineries, oil and gasoline storage and distributing facilities, and the like. Pursuant to the invention, separate liquid handling devices, each in the nature of a vessel or canister and having liquid trapping and ejecting facilities that are free of mechanical pumping action, are employed for raising the ground water and liquid hydrocarbons that accumulate on the ground water table, respectively, through which the well or wells extend, and under the static pressure of the compressed air. The indicated devices are suspended in the same or adjacent wells that are located at the site, with the ground water handling device being connected to a source of compressed air and piping for carrying away the water to form a cone of depression at the site, and the hydrocarbon handling device being connected to the source of compressed air and a recovery line for separately surfacing and conveying the hydrocarbons to a point of collection and recovery. The invention also provides for use of one of the vessels and associated equipment to pump both liquids from the well to the ground surface for separation of same by a conventional separator.
U.S. Pat. No. 4,497,370 (Breslin) discloses an apparatus and method for recovery of liquid hydrocarbons on ground water in which one or more perforate, small diameter well casings are installed in the ground in or at least adjacent to a contaminated soil area containing the liquid hydrocarbons. A liquid recovery unit is in each well casing and each recovery unit has a hollow housing covered by a semi-permeable membrane which passes liquid hydrocarbons but blocks the flow of ground water into the housing. The liquid hydrocarbons collected in the housings can be moved to a receiver by pressurizing the housings, by suction applied to the housings, by pressurizing the well casings, and by the use of submersible pumps near the housings.
U.S. Pat. No. 4,392,532 (Raggio) discloses a method for locating gas lift valves in properly spaced manner within a string of production tubing extending to a production zone within a well. During calculations for valve spacing and set pressures, the spacing and reopening pressures of the valves are corrected to the lowest temperature that is expected to be encountered at any valve while lifting from the next lower valve of the gas lift valve and piping system. An average between the flowing temperature corresponding to the rate to be produced from the next deepest valve and the geothermal temperature gradient are employed to calculate the reopening pressure of any given valve.
U.S. Pat. No. 5,031,697 (Wellington et al.) discloses a method for troubleshooting gas lift wells, to identify whether gas lift valves on the production tubing are open or closed, without the use of wireline tools. The method may also be used to detect leaks in the production tubing or in the well casing. A quantity of a tracer gas is injected into the lift gas at the wellhead, and its return in fluid produced from the well is monitored as a function of time. The tracer's return pattern may be correlated with the depth of entry points and volumes of lift gas entering along the length of the production tubing.
U.S. Pat. No. 5,076,360 (Morrow), the disclosure of which is totally incorporated herein by reference, discloses a method and apparatus for vacuum extraction of contaminants from the ground which, in a preferred embodiment, involves vacuum withdrawal of liquid and gaseous phases as a common stream, separation of the liquid and gaseous phases, and subsequent treatment of the separated liquid and gases to produce clean effluent. A primed vacuum extraction employs a single vacuum generating device to remove contaminants in both the liquid stream and soil gases through a single well casing utilizing a priming tube which introduces air or other gas to the liquid collected at the bottom of a well, permitting vacuum extraction of both liquids and gases from the subsurface by way of wells having a liquid layer which is more than thirty feet below the soil surface or in which a screened interval of the extraction pipe is entirely below the liquid surface.
U.S. Pat. No. 5,050,676 (Hess et al.) and U.S. Pat. No. 5,197,541 (Hess et al.), the disclosures of each of which are totally incorporated herein by reference, disclose an apparatus and process for extracting contaminants from soil both above and below the water table. The process comprises placing a perforated riser pipe in a borehole in a selected portion of the contaminated area, wherein the perforations of the riser pipe are situated below the water table. Optionally, some of the perforations in the riser pipe can also be situated in the vadose zone above the water table. A vacuum is then applied to the pipe to draw gases and liquids from the soil into the pipe and to transport the gases and liquids to the surface as a common stream. At the surface, the common stream is separated into a primarily liquid stream and a primarily gaseous stream, and the separated streams are then treated separately.
U.S. Pat. No. 5,172,764 (Hajali et al.), the disclosure of which is totally incorporated herein by reference, discloses a process for removing contaminants from a contaminated area of the ground having a vadose zone and a water table which comprises providing a borehole in the contaminated area; placing in the borehole a perforated riser pipe inside of which is situated a vacuum extraction pipe with an opening situated near, at, or at any point below the water table within the perforated riser pipe; while introducing a gas into the riser pipe, applying a vacuum to the vacuum extraction pipe to draw gases and liquid from the soil into the perforated riser pipe and from the riser pipe into the vacuum extraction pipe and transport both the gases and the liquid to the surface as a common stream; forming from the common stream a stream which is primarily liquid and a stream which is primarily gaseous; and separately treating the separated liquid and gas streams. Also disclosed is an apparatus for carrying out the process.
Copending application U.S. Ser. No. 08/056,349, filed Apr. 30, 1993, entitled "Improved Process and Apparatus for High Vacuum Groundwater Extraction," with the named inventors Alfonso R. Mancini, Ronald E. Hess, Richard A. Williams, Douglas J. Montgomery, and Heinrich J. Jurzysta, the disclosure of which is totally incorporated herein by reference, discloses a process and apparatus in which vacuum extraction is used to remove soil contaminants in both the saturated and vadose zones. One embodiment of the invention is directed to a process for removing contaminants from a contaminated area of the ground having a vadose zone and a water table, which comprises providing a borehole in the contaminated area to a depth below the water table; placing in the borehole to a depth below the water table a perforated riser pipe inside of which is situated a vacuum extraction pipe with a bottom opening situated within the perforated riser pipe, said vacuum extraction pipe containing groundwater prior to application of a vacuum thereto, said vacuum extraction pipe having at least one gas inlet situated below the groundwater level in the vacuum extraction pipe; while introducing a gas into the riser pipe, applying a vacuum to the vacuum extraction pipe to draw gases and liquid from the soil into the perforated riser pipe and from the riser pipe into the vacuum extraction pipe and transport both the gases and the liquid to the surface as a two-phase common stream; introducing a gas into the vacuum extraction pipe at a level below the groundwater level in the vacuum extraction pipe to initiate two-phase flow within the vacuum extraction pipe; forming from the common stream a stream which is primarily liquid and a stream which is primarily gaseous; and separately treating the separated liquid and gas streams. Also disclosed is an apparatus for carrying out the process.
Copending application U.S. Ser. No. 08/235,571, filed Apr. 29, 1994, entitled "High Vacuum Extraction of Soil Contaminants Along Preferential Flow Paths," with the named inventors Eliott N. Duffney, Paul M. Tornatore, Scott M. Huber, and Ronald E. Hess, the disclosure of which is totally incorporated herein by reference, discloses a process for removing contaminants from a contaminated area of the ground comprising soil having a first permeability, said ground having a plurality of paths of preferential flow, each path having a permeability at least ten times greater than the first permeability, which process comprises providing a borehole in the contaminated area to intersect at least a first path of preferential flow and a second path of preferential flow, said second path of preferential flow being situated at a depth greater than said first path of preferential flow; placing in the borehole a first vacuum extraction pipe having a bottom opening situated within the first path of preferential flow and a second vacuum extraction pipe having a bottom opening situated within the second path of preferential flow; isolating the first path of preferential flow from the second path of preferential flow so that a vacuum applied to the first vacuum extraction pipe with a bottom opening situated in the first path of preferential flow will extract gases and liquids from the first path of preferential flow but not from the second path of preferential flow and a vacuum applied to the second vacuum extraction pipe with a bottom opening situated in the second path of preferential flow will extract gases and liquids from the second path of preferential flow but not from the first path of preferential flow; applying a vacuum to at least one of the vacuum extraction pipes to draw gases and liquid from at least one of the paths of preferential flow into a vacuum extraction pipe and transport both the gases and the liquid to the surface as a common stream; forming from the common stream a stream which is primarily liquid and a stream which is primarily gaseous; and removing contaminants from at least one of the liquid stream and the gaseous stream. Also disclosed is an apparatus for carrying out this process.
Copending application U.S. Ser. No. 08/236,791, filed Apr. 29, 1994, entitled "Apparatus and Process for Treating Contaminated Soil Gases and Liquids," with the named inventors Eliott N. Duffney, Paul M. Tornatore, Scott M. Huber, and Ronald E. Hess, the disclosure of which is totally incorporated herein by reference, discloses an apparatus for extracting contaminants from a stream comprising a contaminant-containing mixture of liquids and gases which comprises: (a) a contaminant-containing mixture input; (b) a vapor-liquid separator receiving the contaminant-containing mixture from the input and producing a liquid component stream at a first outlet and a gaseous component at a second outlet; (c) an optional first contaminant removal system receiving the liquid component stream from the vapor-liquid separator and producing a contaminant-free liquid stream; (d) a vacuum inducing device in fluid communication with the contaminant-containing mixture input and the vapor-liquid separator and receiving said gaseous component from the vapor-liquid separator; (e) a cooling element receiving the gaseous component at a first temperature from the vacuum inducing device and producing the gaseous component at a second temperature from a first outlet and a condensed liquid component from a second outlet, said second temperature being lower than said first temperature; (f) a heating element receiving the gaseous component from the cooling element at said second temperature and producing a reduced-relative-humidity gas component at a third temperature, said third temperature being higher than said second temperature, said heating element having a heating jacket surrounding a conduit through which the gaseous component passes through the heating element, said heating jacket receiving a heating fluid from a first heat fluid conduit into a heating jacket input and outputting said heating fluid from a heating jacket outlet into a second heating fluid conduit; and (g) an optional second contaminant removal system receiving the reduced-relative-humidity gas component from the heating element and producing a contaminant-free gas; wherein the apparatus necessarily includes either the first contaminant removal system or the second contaminant removal system.
Although known apparatuses and processes are suitable for their intended purposes, a need remains for a process and apparatus for removing contaminants from groundwater and soil which enables contaminant removal from below and/or above the water table. A need also remains for a process and apparatus for removing contaminants from groundwater and soil which enables contaminant removal from soils of varying air permeability and varying porosity. Further there is a need for a process and apparatus for removing contaminants from groundwater and soil which enables increased flexibility in the location of extraction wells. A need also exists for a process and apparatus for removing contaminants from groundwater and soil that enables vacuum extraction of contaminants through a well from below the water table when the water table is deeper than the equivalent lift of the vacuum pump connected to the well. There is also a need for a process and apparatus for removing contaminants from groundwater and soil with simplified equipment in that a single vacuum pump can be employed to remove contaminants in both the vapor and liquid phases through a single well or pipe. Additionally, there is a need for a process and apparatus for removing contaminants from groundwater and soil that enables reduction of contaminant concentrations in the extracted groundwater as a result of the mixing of air and water in the vacuum extraction pipe, leading to reduced subsequent water treatment requirements. In addition, there is a need for a process and apparatus for removing contaminants from groundwater and soil that dewaters the saturated zone (groundwater) in the vicinity of the extraction well in some soil conditions, thereby allowing air flow to move through the dewatered soil, which accelerates the extraction rate of contaminants and results in reduced cleanup time. Further, there is a need for a process and apparatus for removing various kinds of contaminants from groundwater and soil, including volatile materials, nonvolatile materials, metal contaminants, and the like. A need also remains for a process and apparatus for removing soil contaminants with improved, faster contaminant removal rates. There is also a need for apparatus and processes for removing soil contaminants through a vacuum extraction tube in a well wherein the depth of the extraction tube in the well can be easily adjusted. Further, there is a need for apparatus and processes for removing soil contaminants via a vacuum extraction process wherein the contamination of the vacuum source and processing equipment is reduced or eliminated.